PROJECT SUMMARY DAT18-08. The criminal justice setting holds great promise for identifying people with opioid use disorder and providing access to evidence-based treatment. However, the impact of expanded access to MAT in prisons and jails on post-release rates of overdose has not been explored on a large scale, and the population health impacts associated with varied MAT interventions in CJ settings are unknown. Therefore, novel approaches are urgently needed to determine the impact of expanded MAT access on rates of fatal overdose in the CJ- involved population. The following specific aim is proposed to supplement and expand the scientific impact of the parent grant: To estimate the impact of expanded access to MAT in prisons and jails on post-release rates of overdose. Our approach will use agent-based modeling, data collected through the parent study, existing surveillance data in RI, and recently-published data from similar settings to understand how different MAT interventions in prison and jail setting impact overdose death post-release. We will examine the impact of the following interventions on post-release rates of overdose: (1) standard of care/no intervention; (2) providing access to depot-naltrexone alone; (3) providing access to all three MATs to only those who were prescribed it prior to incarceration; and (4) comprehensive provision of all three MATs. These interventions were selected for evaluation because they represent the most commonly utilized approaches to MAT provision and one idealized care case. These models will incorporate advanced methodological techniques that will allow for the investigation of engaged treatment, program attrition, and other complex events on a population-level. We will develop an agent-based model using historical data on overdose fatality rates in Rhode Island (RI) to forecast the number of opioid overdose fatalities over an eight year period (2017-2025) under four different MAT strategies. State surveillance data from the four years preceding implementation of the comprehensive MAT program (2012-2016) will be used to calibrate the model. In order to compare the different strategies, we will calculate and compare the total number of overdose fatalities statewide as well as the number of overdose fatalities among those being released from correctional facilities over the eight year period. The ABM will be calibrated to data available through the collaboration to accurately reflect real-world trends in incarceration, access to treatment, and overdose fatalities. Published studies, with a priority for those based in Rhode Island, will be used to parameterize the model regarding the demographics of incarceration and overdose, the probability of overdose, and other key parameters. We expect that the findings from this study may be used by health agencies, policy makers, and correctional systems to inform their efforts to expand MAT access.